Chapter 7 Skeleton

Chapter 7 Skeleton - 1 2 3 4 5 6 7 8 9 10 The Skeletal...

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1 The Skeletal System Functions Support Protection of soft organs Movement Storage of minerals Site of blood cell formation The Skeletal System 206 bones in 2 divisions Axial Skeleton 80 bones Skull (cranium + facial bone) Trunk (vertebral column + thorax) Appendicular Skeleton 126 bones Extremities + Classification of Bones Gross Anatomy of Long Bone Bone Marrow Yellow marrow In the central cavities of the long bone Composed largely of fat Red marrow In spongy bone Manufactures at birth, red marrow is present throughout the skeleton; by 20-25 years, red marrow conversion to yellow marrow is usually complete Microscopic Anatomy of Bone Types of Osseous Cells Osteoblasts (-blast = immature) Bone-building cells Manufacture extracellular matrix Active in embryonic cartilage Osteocytes : Mature bone cells Osteoblasts osteocytes once the matrix has hardened Maintain bone matrix Osteoclasts (-clast = to break) Bone-breaking cells Develop from monocytes (a WBC) Ossification : Formation of bone from cartilage By osteoblasts Ossification develops during embryonic life from embryonic cartilage to produce matrix to start the ossification process Resorption : Demineralization of bone, i.e. release of Ca into the blood By osteoclasts 2 3 4 5 6 7 8 9
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2 Ossification of Long Bones Epiphyseal Line Secondary bone-forming centers, the epiphyseal plates , develop across the end of bones Epiphyseal plates harden when bone formation is complete epiphyseal line (seen on X- rays) Adult bone is continuously being remodeled in response to the stresses put on it Why do children recover from fractures faster than adults? Ossification & resorption of bone tissue is regulated by vitamin D (a fat soluble steroid hormone) Lack of vitamin D results in bone malformation. ... WHY? Bone Markings: Projections Head : a rounded, knoblike end separated from the rest of the bone Crest : distinct ridge, often rough e.g. over the top of ilium Spine : a sharp projection from the surface of the bone e.g. spine of the scapula (shoulder blade) Bone Depressions Foramen: (plural =foramina) a hole in the bone allows a blood vessel or a nerve to pass through or between bones Fossa : a depression on a bone surface Sinus : An air space found in some skull bones Bones of the Skeleton Table 7-1 The Axial Skeleton Vertical axis of the body, composed of : Skull Cranium (8 cranial bones) Facial bones (14 bones) Vertebral column Bony thorax
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Chapter 7 Skeleton - 1 2 3 4 5 6 7 8 9 10 The Skeletal...

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